DESCRIPTION (applicant's abstract): The aim of this research is to study the structure and function of two membrane enzymes and transporters. The objective is to understand the function of these membrane proteins at the molecular level and to describe the biological significance of their activity. The structure and function of the ectoapyrases, membrane-bound enzymes present on all animal and many higher eukaryotic cells, will be explored using the methods of biochemistry, cell biology and genetics. The ultimate aim is to determine the physiological function of the enzyme : what is the benefit to the organism of extracellular nucleotide hydrolysis. The identification, isolation, and characterization of non-mitochondrial transport systems for AT? in animal and yeast cells will be carried out. The question of interest is the structure of the transporters that effect net transport of the nucleotide across membranes : are these a new class of proteins or are they already known. The ultimate aim is to understand the physiological significance of the nucleotide efflux. The information obtained by this research will illuminate the significance of ATP (and other nucleotide) metabolism at the outer surface of the plasma membrane, with particular reference to the interplay of the activities of the AT? transporter and the ectoapyrase. Some central questions are whether ATP release is only used as signal for purinergic receptors which is subsequently terminated by the ectoapyrases, or is AT? extrusion part a way to regulate the amount of the nucleotide at the plasma membrane. The aim of this research is to study the structure and function of two membrane enzymes and transporters. The objective is to understand the function of these membrane proteins at the molecular level and to describe the biological significance of their activity. The structure and function of the ectoapyrases, membrane-bound enzymes present on all animal and many higher eukaryotic cells, will be explored using the methods of biochemistry, cell biology and genetics. The ultimate aim is to determine the physiological function of the enzyme : what is the benefit to the organism of extracellular nucleotide hydrolysis. The identification, isolation, and characterization of non-mitochondrial transport systems for AT? in animal and yeast cells will be carried out. The question of interest is the structure of the transporters that effect net transport of the nucleotide across membranes : are these a new class of proteins or are they already known. The ultimate aim is to understand the physiological significance of the nucleotide efflux. The information obtained by this research will illuminate the significance of ATP (and other nucleotide) metabolism at the outer surface of the plasma membrane, with particular reference to the interplay of the activities of the AT? transporter and the ectoapyrase. Some central questions are whether ATP release is only used as signal for purinergic receptors which is subsequently terminated by the ectoapyrases, or is AT? extrusion part a way to regulate the amount of the nucleotide at the plasma membrane.